1. Field of the Invention
The invention relates in general to a one-time-programmable (OTP) memory device and method for testing the same, and more particularly to an OTP memory device and method for testing the same, in which a first program operation is performed to check the memory device and test-pass memory device is supplied to a user without erase operation.
2. Description of the Related Art
For one-time-programmable (OTP) products such as oxide-nitride-oxide read only memory (NROM) devices, technical engineers usually need to use a normal program algorithm to check whether each memory cell on the whole chip can have a good operation. One way to test the memory device is to program a row and a column of test memory cells on the chip. The whole memory array is determined to be good if data can be written into the test memory cells successfully during programming. Although this test method is time-saving, the test result is indeed unreliable for it cannot verify all the memory cells on the chip are good.
Another method to test the memory device is to program the whole array cells. After the test program operation, an erase operation is performed on that chip in order to clear the memory cells for user program. Usually, two or three program-and-erase cycles are required to achieve the test purpose. The erase operations increase the charge loss in programming and consequently the NROM device needs ten times cycling margins for a program operation, thereby reducing the quality of the memory device. In the meanwhile, the size and cost of the memory device is increased due to extra erase circuits for erase function disposed on the chip.